Communication disorders in infancy and childhood are frequently characterized by interactions between the mechanisms of speech, hearing, language, and learning. Research to be conducted in this program is focussed on disorders manifested by abnormal or delayed development of two or more aspects of communication. Complex communication problems demand multiple scientific and clinical specialties to determine the fundamental causes and nature of the underlying disorders, to develop effective treatments and, ultimately, to avoid the occurrence of those problems. Specific projects included in this program are the study of speech disorders, disorders of auditory development, of impaired cochlear function, and of the ability to discriminate sounds with the complexity of human speech. An additional project, which interacts with each of the first four, is the determination of the degree to which these disorders are caused by pre- or postnatal environmental factors, or are genetic in origin. These projects represent the clinical research effort of an institute in which physicians, speech, language, and hearing clinicians, and psychologists provide in- and out-patient services for communicatively impaired children, and scientists from eight disciplines conduct laboratory research aimed at a better understanding of the fundamental nature of communication disorders.